Problems with thin protein crystals

Zbyszek Otwinowski zbyszek at mix.swmed.edu
Thu Feb 27 13:45:23 EST 1997


Steffen Graether wrote:
> 
> Hello,
> 
>         We have been able to get thin (>0.05 mm) crystals that grow
> relatively well in the other two dimensions, but this results in weak
> diffraction patterns (~5000 s exposure per frame). Coventional seeding
> techniques fail. Could anyone provide suggestions and ideas on how I could
> grow thicker crystals?
>         In addition, the diffraction pattern across the top and bottom of
> the frame have reflections that are badly split (more like smears),
> while those across the middle are round.

This is typical of crystals with very high mosaicity.

> Can anyone suggest a way to
> reject the poor areas of the frame so that we could extract the good
> data? We use mainly denzo and scalepack but mosflm and ccp4 are also
> available.
> 

Ignore quadrilateral in denzo would work.
Also resolution limits, as large mosaicity may lead to many overlaps
at high resolution. Practical upper limit to mosaicity is about 1.5
degreein denzo, in some cases even 2-2.5 degree mosaic crystals have
been processed.

-- 
  Zbyszek Otwinowski                     |        zbyszek at chop.swmed.edu
  University of Texas                    |        tel : (214)-648-5098 
  Southwestern Medical Center            |        fax : (214)-648-5095 
  5323 Harry Hines Boulevard  Dallas, Texas  75235-9038
[EOB]




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